I quite like looking at the chin/mouth area. I can see the shoulders, eyes, gloves, upper body, even footwork in peripheral vision if you have your chin nicely down.

For me as a beginner I can tell the punches coming easiest by a combination of gloves from peripheral vision and a twitch of the shoulders/upper body. I would never look directly at the gloves and attempt to follow them, as Barry says, that's asking to be tricked.

As for looking directly into the eyes, I find this a little off putting and kind of takes your concentration away from what's going on. But maybe this is a more advanced technique, a more subtle one.